1. Field of the Invention:
The present invention relates to a flexible arm for use in an industrial robot or a programme controlled manipulator.
2. Description of the Prior Art:
There has been known a programme controlled manipulator comprising a support post mounted on a turntable, an arm swingably attached to one end of the support post, and a paint spray gun or nozzle carried on a free end of the arm so that the paint spray gun can automatically be brought to a desired position by angularly moving the support post and the arm for performing painting operation.
The known arm of the manipulator is generally not freely bendable, rendering it relatively difficult to control the paint spray gun to be brought into any desired position. Therefore, the conventional manipulator arm can work only with work-pieces of relatively simple configurations, and has found limited use.
Various bendable or flexible manipulator arms have been proposed in the recent past. However, the proposed arms are complex in construction, and where there are relatively long, they tend to flex by their own weight, resulting in a difficulty to place the spray nozzle in a desired position. One way to cope with this problem would be to assemble the arm of highly rigid parts, but such an arrangement would not be practically preferable.
The proposed manipulator arms are flexibly bendable only through limited angular intervals or distances by corresponding displacements of actuators, and hence fail to operate efficiently or make the most use of the advantages accruing from the bendability of the arms.
The actuator in most applications is mounted on the base and operatively connected through a universal joint to the paint spray nozzle serving as a tool mounted on the free end of the arm for transmitting rotation from the actuator to the spray nozzle. With the nozzle coupled to the actuator via the universal joint, operation of the nozzle is adversely affected by a backlash or play in the universal joint. Unless such a backlash is reduced to a large degree or virtually eliminated, an angular displacement of the nozzle does not conform with the angular displacement of the actuator that has produced the nozzle displacement, failing to bring the nozzle to a desired angular position. This problem becomes worse especially when the arm is used on teaching-playback type manipulators, in that positioning the spray gun upon playback based on positional data obtained during teaching operation often fails to bring the spray gun precisely to a desired position determined upon teaching.